1. Field of the Invention
This invention relates to a planar light source device, more particularly to a planar light source device including a plurality of light-emitting diode chips disposed in a matrix array.
2. Description of the Related Art
Referring to FIG. 1, Taiwanese Patent Publication no. 289947 discloses a planar light source device including a substrate 92 and a plurality of light-emitting diode chips 91 disposed in a matrix array on the substrate 92. Each of the light-emitting diode chips 91 has a size smaller than 40 mil (1 mm) (in particular, from 8 mil (0.2 mm) to 14 mil (0.35 mm)). The light-emitting diode chips 91 are connected directly to a circuitry formed on a metal layer of the substrate 92 to enhance heat conduction and light emission efficiency.
However, in practice, the distance between two adjacent ones of the light-emitting diode chips 91 and the thickness of the substrate 92 tend to affect heat dissipation and light-emitting efficiency of the planar light source device. This problem is not addressed in the Taiwanese patent publication.